Process for weighting silk



' Patented June 19, 1928.

UNITED STATES 1,674,356 PATENT OFFICE.

EGON' ELOD, OF KARLSRUHE, GERMANY, AS SIGNOR T0 FIRM OF RUDOLPH KOEPP &;

00., OF OESTRICH-ON-THE-RHINE, GERMANY, A SOCIETY OF GERMANY. I

PROCESS FOR WEIGHTING SILK.

No Drawing. Application filed November 2, 1922, Serial No. 598,671, and in Germany November 14, 1921.

Silks weighted with stannic chloride presents the inconvenience that they rapidly deteriorate and become brittle when exposed to light and air, this being due to the presence of hydrochloric acid liberated during the weighting process. It has been suggested to obviate this difliculty by subsequently treating the weighted silk with various substances such as sulpho cyanate, thiosulphate, aldehydes and the like, but this procedure has not given perfectly satisfactory results. The use of organic tin salts as weighting substances is disadvantageous because but few organic tin salts, adapted for silk weighting, can'be isolated as independent and stable substances. Furthermore, silk fibers absorb but little tin from solutions of the easilyobtainable basic salts of organic acids so that weighting within the usual degrees'is impossible. The silk fibers so treated also lose their glossy character. Both disadvantages are due tothe fact that the tin salts of organic acids, in aqueous solution, hydrolyze to form colloidal stannic acid. This stannic acid will I not diffuse into the silk fiber substance and only deposits upon the surface of the fibers.

According to the present invention, the weighting of silk is efiected by incorporating in the silk fiber easily hydrolyzed double salts of tin with organic acids, for instance, formic, acetic, lactic acid and the like. The hitherto unknown double salts of tin with organic acids, especially formic acid, have proved to be'especial-ly suitable. for weighing purposes. For instance, the double salt of formic acid with tin and sodium, that is, disodiumstannic-hexaformate, is an advantageous material touse. It may be made by treating sodium formate with stannic chloride in aqueous solution according to the following reaction:

6HCOONa+SnCl,+aqua-.-

Na sn (HQOO) ,,.5H O 4NaCl aqua.

Other alkali formates can be used.

One of the best ways of carrying out my invention is to produce the double salts of tin in the silk fiber. This can be done by first impregnating the fiber with a solution of sodium formate and then treating the impregnated fiber in a solution of stannic chloride. By subse uent treatment with water, colloidal stannic acidv is formed within the fiber and the silk preserves its full colloidal stannic acid in the fibers.

gloss. The degree of weighting is even higher than when stannic chloride alone is usedaccording to usual methods. To illustrate this, I have secured 100% weighting of the fiber after four passages through the bath in accordance with my process whereas when using stannic chloride alone, five such passages or treatments are required in order to obtain a similar result. A further advantage in my process is that silk wei hted according to the present invention is c aracterized bygreat resistance tov ripping and tearing even though the silk be exposed for long periods to the action of light and air. Pure unweighted organzine,

possessing a ripping resistance of 61.1 grams, after a 100% weighting according to the present process with sodium formate and stannic chloride, showed a ripping resistance of 61.0 grams. After the weighted silk had been exposed to the influence of light and air for six weeks, the ripping resistance was unchanged. The same silk weighted to the same degree with stannic chloride alone, showed a ripping resistance immediately after the weighting of 53.0 grams. 7

In practice, I prefer to carry out my weighting process by first treating the-silk with a concentrated aqueous solution of an alkali metal formate, such as sodium, po-

tassium, aluminum, or lithium formate and which may contain free acld, such as formic acid or acetic acid. Then, after removing the excess liquids, for instance, by treatment in a centrifuge, I subject to impregnated silk to a short treatment ina solution of stannic chloride until the fibers are com-- pletely saturated. The silk is then hung up and thereafter washed with water to hydrolyze the tin salt. The silk is finally treated with sodium phosphate to, fix lthe be whole operation is advantageously repeated several times and finally,there may be employed a treatment with waterglass or clay.

Instead of 'first treating the fiber with a solution of an alkali metal formate and then with stannic chloride, the. process may be reversed. 'In this case, inasmuch as the detrimental efiect of the hydrochloric acid begins to appear during the impregnation of the silk with stannic chloride, it is advisable to immediately treat the stannic chlorideimpregnated silk with the formate solution.

What I claim is:

I 1. A method for loading silk comprising the steps of incorporating in. the silk fibre a double salt of alkali-metal formate and tin salt and Washing the treated 'silk to hydrolyze the tin salt.

2. A method for loading silk comprising the steps of incorporating in the silk fibre a double salt of alkali-metal formate and tin salt, Washing the treated silk to hydrolyze the tin salt and treating the silk with a fixing material for the stannic acid formed by the hydrolysis.

3. A method for loading silk comprising the steps of successively treating the silk with a solution of an alkali-metal form-ate and with a solution of a tin salt, washing the treated silk to hydrolyze the formed double salt anditreating the silk with a fixing m'aterial for the stannic acid formed by the hydrolysis of the double salt.

4. A method for loading silk comprising 7 the steps of successively treating the silk with a solution of an alkali-metal formate containing free organic acid and with a .soluti'on of a tin salt, washing the treated silk to hydrolyze the formed double salt and treating the silk with a fixing material for the stannic acid formed by the hydrolysis of the double salt.

5. A method for loading silk comprising the steps of successively treating the silk with a solution of sodium formate containing free formic acid and with a solution of stannic chloride, Washing the treated silk to hydrolyze the formed disodium stannic hexaformate and treating the silk hydrolysis of'the disodium stannic hexaformate.

In testimony whereof I aflix my signature.

EGON EIDD.

with a fixing 7 material for the tannic acid formed by the- 

